The present invention is directed to a dental handpiece having a head section, which contains a motor or turbine driven by compressed air, a grip portion extending from the head section to a connecting fitting, which is adapted for connection to a hose which has a compressed air supply line and a separate supply line for each additional agent that is desired. The compressed air and other agents, if present, are conveyed to the head section by interconnected passages which are arranged in the head section, grip portion and connecting fitting of the handpiece.
The present invention proceeds from the fact that the supply hose of a dental handpiece of a known construction produces an interferring torsional moment during manual manipulation of the handpiece of an operator who must compensate for this torsional moment by applying a greater counter-moment with his fingers. In order to avoid this disadvantage, it is known to provide so-called rotary coupling, which is a separate component, between the supply hose and the handpiece. The addition of this coupling or joint provides a further separating point or point in addition to those separation points already present in the known handpiece structures, for example, the joint between the grip portion and the head section. With the addition of this additional component, the cost of producing the handpiece or the handpiece arrangement, respectively, is increased. The presence of this additional component will increase the length of the handpiece and create an additional disadvantage, which is that this lengthening of the handpiece will strongly impair the manipulability of the handpiece.
In addition to the above-mentioned rotational coupling or joint, it is also desirable to provide the dental handpiece with a throttle valve or choker valve in order to enable changing or controlling the pressure of one of the agents. For example, the controlling of the pressure of the compressed air will enable the changing of the number of revolutions of the air driven motor. In order to provide the throttle or choker valve, a known solution provides an intermediate piece or component between the supply hose and the handpiece. The intermediate piece has a rotatable concentric ring and a valve which will vary the flow cross section of a passage in response to rotation of the concentric ring. By the addition of this separate component containing the throttle or choker valve, the handpiece arrangement is further lengthened and is thus extremely unwieldy. As a consequence of the significantly longer lever arm of the handpiece on which the weight of the supply hose is applied, a much greater pitching moment will act on the handpiece and must be compensated by a correspondingly greater counter-force from the operator's fingers grasping the handpiece.